Question

A box contains 100 marbles, some of which are red and the rest blue. A sample of 10 marbles is taken randomly (with replacement) from the box and the statistic: number of red marbles in the sample is calculated. The probability model for this statistic is shown below. (Note: the probabilities should add to 1 - any difference from 1 is due to round-off errors.)

values probability
(%)
0 0.6047
1 4.0311
2 12.0932
3 21.4991
4 25.0823
5 20.0658
6 11.1477
7 4.2467
8 1.0617
9 0.1573
10 0.0105
a. Roughly, what is the shape of the probability model? Write the shape in a complete sentence
b. Calculate the center (mean) of the probability model. Use R as a calculator to calculate the mean. Write the mean in a complete sentence
c. Argue that 1.5 is a good guess for the standard deviation of the probability model. Write a brief answer
d. Suppose you repeat the experiment of sampling 10 randomly with replacement n times. Each time, you calculate the number of red marbles in your sample. Suppose you were to make a plot of the running means of the results, what would happen as n increases?

Answer 1

Explanation:

a) The Roughly shape of the probability model is bell shaped or symmetric

( normal )

(b) Roughly, guess the center (mean) of the probability model

The mean is 5/10 =0.5

Because the symmetric distribution mean is middle bar and here we see using histogram 5/10 is mean .

(c) Argue that 1.5 is a good guess for the standard deviation of the probability model.

Yes 1.5 is very good guess because then it follow normal distribution it is exactly correct .